1. Field of the Invention
The present invention relates to an image forming device such as a printer, a copier, and a facsimile apparatus, and more particularly to an image forming device making it possible to conduct adequate density adjustment control.
2. Description of the Related Art
Image forming devices for forming images by using electrophotographic technology implemented in color printers or the like generally comprise an image carrier for forming an electrostatic latent image correspondingly to image data, a charging unit for charging the outer peripheral surface of the image carrier, an exposure unit for exposing the outer peripheral surface of the electrically charged image carrier and forming an electrostatic latent image, a development device for supplying a toner, which is a developing agent, to the electrostatic latent image and developing the toner image, and a transfer unit for transferring the toner image on the medium which is a transfer object.
In such an image forming device, a processing called image density adjustment is usually conducted so that the image output can be always conducted at a good image density. This density adjustment is conducted when characteristics relating to toner image formation on the image carrier supposedly change, for example, when the power source of the image forming device is turned on, after the execution of the prescribed number of image formation cycles, or when the image carrier is replaced. Further, this density adjustment is conducted by creating a pattern in the form of patches or fine lines under each operation condition on the image carrier, detecting the pattern density with a sensor, and conducting feedback to the operation conditions. For example, a development bias applied to the roller section of the toner cartridge accommodating the toner, which is provided in the development device, is varied and paint-out patches are produced at each bias value. Further, the density of each patch that was thus formed is measured, the development bias value at which the desired density value is assumed is found from those values, and the control is so conducted that this value is assumed.
Several methods for controlling such density adjustment have been suggested. In the device described in Japanese Patent Application Laid-open No. 2003-345180, a control method is employed by which when the device is set in a speed priority mode, the device start-up operation is conducted without executing the density adjustment and the time to image output is shortened.
On the other hand, among the toner cartridges mounted on the developing device, there are toner cartridges that guarantee that the image forming device can demonstrate the performance inherent thereto when the toner cartridge is mounted, that is, the toner cartridges manufactured and marketed, e.g., by the manufacturer of the image forming device, and other toner cartridges, that is, toner cartridges that were neither manufactured nor marketed by the manufacturer of the image forming device. The toner cartridges of the former group will be called hereinbelow the products whose quality was guaranteed by the manufacturer of the image forming device such as a printer and the toner cartridges of the latter group will be called the products whose quality has not been confirmed by the manufacturer of the image forming device such as a printer. In principle, the products of guaranteed quality have to be mounted and used in the image forming devices, but because the products whose quality has not been confirmed by the manufacturer are also marketed, the users sometimes mount and use those products whose quality has not been confirmed by the manufacturer.
As described hereinabove, the operation of density adjustment control has been conducted in image forming devices, but such a control did not take into account whether or not the toner cartridge mounted on the image forming device is the above-described product of guaranteed quality.
In the usual cases, it is assumed that a toner cartridge that is a product of guaranteed quality is mounted on the image forming device. Therefore, the above-described density adjustment is also controlled based on the contents suitable for the toner cartridge of guaranteed quality, for example, so that in the above-described adjustment of development bias, the processing is executed according to a range suitable for products with guaranteed quality. Therefore, in the conventional devices, even when a toner cartridge whose quality has not been confirmed by the manufacturer is mounted, because this fact is not taken into account, the density adjustment is conducted based on the same contents as that for the products of guaranteed quality. Generally, the toner cartridges themselves and properties of toners accommodated therein sometimes differ between the products of guaranteed quality and products whose quality has not been confirmed by the manufacturer. Therefore, sometimes the density adjustment is not conducted by the same method. In this case, as described above, if a product whose quality has not been confirmed by the manufacturer is mounted, the density adjustment processing generates an error and processing is interrupted. Further, even if the density adjustment processing ends without generating an error, good adjustment results sometimes cannot be obtained. Thus, problems are still associated with the density adjustment control in the conventional devices.